Monica Marchese1, David Cowan2, Elizabeth Head3, Donglai Ma4, Khalil Karimi2, Vanessa Ashthorpe5, Minesh Kapadia6, Hui Zhao6, Paulina Davis3, Boris Sakic6. 1. Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada. 2. Department of Medicine, McMaster University, Hamilton, ON, Canada. 3. Department of Molecular & Biomedical Pharmacology, Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA. 4. Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada. 5. Central Animal Facility, McMaster University, Hamilton, ON, Canada. 6. Department of Psychiatry & Behavioral Neurosciences, McMaster University, Hamilton, ON, Canada.
Abstract
BACKGROUND: Immune system activation is frequently reported in patients with Alzheimer's disease (AD). However, it remains unknown whether this is a cause, a consequence, or an epiphenomenon of brain degeneration. OBJECTIVE: The present study examines whether immunological abnormalities occur in a well-established murine AD model and if so, how they relate temporally to behavioral deficits and neuropathology. METHODS: A broad battery of tests was employed to assess behavioral performance and autoimmune/inflammatory markers in 3xTg-AD (AD) mice and wild type controls from 1.5 to 12 months of age. RESULTS: Aged AD mice displayed severe manifestations of systemic autoimmune/inflammatory dise6ase, as evidenced by splenomegaly, hepatomegaly, elevated serum levels of anti-nuclear/anti-dsDNA antibodies, low hematocrit, and increased number of double-negative T splenocytes. However, anxiety-related behavior and altered spleen function were evident as early as 2 months of age, thus preceding typical AD-like brain pathology. Moreover, AD mice showed altered olfaction and impaired "cognitive" flexibility in the first 6 months of life, suggesting mild cognitive impairment-like manifestations before general learning/memory impairments emerged at an older age. Interestingly, all of these features were present in 3xTg-AD mice prior to significant amyloid-β or tau pathology. CONCLUSION: The results indicate that behavioral deficits in AD mice develop in parallel with systemic autoimmune/inflammatory disease. These changes antedate AD-like neuropathology, thus supporting a causal link between autoimmunity and aberrant behavior. Consequently, 3xTg-AD mice may be a useful model in elucidating the role of immune system in the etiology of AD.
BACKGROUND: Immune system activation is frequently reported in patients with Alzheimer's disease (AD). However, it remains unknown whether this is a cause, a consequence, or an epiphenomenon of brain degeneration. OBJECTIVE: The present study examines whether immunological abnormalities occur in a well-established murineAD model and if so, how they relate temporally to behavioral deficits and neuropathology. METHODS: A broad battery of tests was employed to assess behavioral performance and autoimmune/inflammatory markers in 3xTg-AD (AD) mice and wild type controls from 1.5 to 12 months of age. RESULTS: Aged ADmice displayed severe manifestations of systemic autoimmune/inflammatory dise6ase, as evidenced by splenomegaly, hepatomegaly, elevated serum levels of anti-nuclear/anti-dsDNA antibodies, low hematocrit, and increased number of double-negative T splenocytes. However, anxiety-related behavior and altered spleen function were evident as early as 2 months of age, thus preceding typical AD-like brain pathology. Moreover, ADmice showed altered olfaction and impaired "cognitive" flexibility in the first 6 months of life, suggesting mild cognitive impairment-like manifestations before general learning/memory impairments emerged at an older age. Interestingly, all of these features were present in 3xTg-ADmice prior to significant amyloid-β or tau pathology. CONCLUSION: The results indicate that behavioral deficits in ADmice develop in parallel with systemic autoimmune/inflammatory disease. These changes antedate AD-like neuropathology, thus supporting a causal link between autoimmunity and aberrant behavior. Consequently, 3xTg-ADmice may be a useful model in elucidating the role of immune system in the etiology of AD.
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